While total hip replacement is one of the most successful operations, after a period
of 10 – 15 years it can fail like any mechanical device. This may require further
revision surgery which is often a more complex than a primary total hip replacement
(first time hip replacement). Revision surgery is technically difficult and often
involves removing the old hip replacement and replacing with a more complex hip replacement.
The surgeon also has to restore the bone stock with bone grafts or special artificial
materials.

As more and more younger people are being offered hip replacements and the number
of hip replacements are increasing, it is likely that the number of revisions will
also increase in the future. Mr.Ganapathi employs up-to-date techniques in improving
the outcomes for these difficult and challenging problems. While it would be possible
to do revision surgery in majority of the patients with improvement in function,
it is important to understand that the complication rates are higher than primary
hip replacement. The medical co-morbidities also need to be taken into account to
assess the risk of revision surgery. Mr.Ganapathi would discuss those issues with
you and if appropriate would also ask for a pre-anaesthetic assessment before a decision
is made about revision surgery.

There are several ways in which a total hip replacement can fail including:

With time, the plastic in the cup side of the total hip replacement becomes worn
out. In that process tiny plastic particles are produced to which the surrounding
tissues react. This reaction leads to the bone getting gradually eaten away (lysis)
leading to loosening of the hip replacement. The hip becomes painful. Pain can be
present in the hip in the region of the groin or it can present as thigh pain. Sometimes
the loosening may be relatively asymptomatic for a long time and becomes only very
symptomatic when there is large amount of bone destruction which makes the revision
procedure even more complex. This is one of the reasons for regularly following the
hip replacement patients with x-rays through their lifetime.

2. Dislocation

The ball of the total hip replacement may come out of the socket. This can occur
at an early stage or at a late stage. There are a number of reasons for dislocation
to occur. Usually it would be possible to put the hip back into the joint (often
will need an anaesthetic). If the dislocation keeps recurring, it would be appropriate
to consider revision procedure. Mr. Ganapathi was involved in a study analysing the
financial aspect and functional improvement following in patients with first time
dislocation of the hip. On a conservative estimate, the financial cost in subsequent
management of 100 first time dislocating hips was over £500000 and the functional
improvement was less than optimal. One of the reason for dislocation is the fact
that the ball of the total hip replacement is much smaller than the native ball of
the hip joint. This compromise was taken as the properties of the materials available
in the past did not suit larger size heads. However, there are various modern material
available (like metal, ceramic and special plastics) which allow a bigger size ball
to be used during the hip replacement. Studies have shown that the there is less
dislocation rates as the ball size increases. The UK national registry also shows
that there is an increasing trend among the hip surgeons to use relatively larger
ball in the recent years.

3. Infection

Infection following hip replacement is a very rare complication. It can occur soon
after surgery (early infection) or many years after the hip replacement (late infection).
Early infection can be superficial or deep. While the former may respond to antibiotics,
the deep infection will need further surgery in the form of washout or revision procedure.
Late infection can occur at anytime throughout the lifetime due to bacteria (bugs)
entering the blood stream from infection in other parts of the body. If this happens,
the hip replacement gradually gets loose and the hip becomes painful. Although it
is a challenging problem, majority of the patients could be treated by revision surgery.
This usually is a two stage procedure with the first stage being removal of the infected
hip replacement and insertion of temporary spacer and treatment with antibiotics
followed by second stage with a definitive hip replacement (when the infection has
settled – usually after 3 months).

4. Periprosthetic fracture

This is a rare complication following hip replacement. The bone fractures (breaks)
around the vicinity of the hip replacement. Depending on the type of fracture, this
may be treated by internal fixation or by further revision surgery with a complex
hip replacement.

5. Failure of bone in-growth into the implants

This can occur in some cases of uncemented implants if there is not enough host bone
contact with the implants (usually in the acetabular component) or if there is not
enough vascularity for the bone growth to occur. Special materials like trabecular
metal (made of tantallum) are now available which have a porous structure similar
to cancellous bone and has better osteointegration properties than conventional titanium
implants and hence being increasingly used in revision hip replacement.

6. Abductor Failure

This is quite a challenging problem and more commonly associated with lateral approach.
Often the failure is due to the fact that the abductor muscle is quite weak and is
not able to hold the sutures. This can give an abnormal gait and in addition, this
can also be a factor resulting in recurrent dislocation. Revision surgery often involves
some form of constrained/captured device to hold the ball in place. While it may
be possible to reattach the abductor muscle, it is not always successful.

Scientific Literature

The following are some relevant selected scientific references:

1. Trends in the number of knee and hip arthroplasties: considerably more knee and
hip prostheses due to osteoarthritis in 2030.

Abstract: OBJECTIVE: To predict the future number of knee and hip arthroplasties
due to osteoarthritis (OA) in the Netherlands based on historical trends and demographic
projections.

DESIGN: Data analysis and model calculations.

METHOD: Two future projections were based on age and sex-specific number of hospital
admissions for the placement of total knee or hip prostheses due to OA between 1995
and 2005; data were obtained from the Dutch National Medical Registration (LMR).
The demographical projection was based on the incidence of arthroplasty in 2005 combined
with demographic predictions from Statistics Netherlands regarding the time period
between 2005 and 2030. The trend projection used the trend in the age and sex-specific
incidence of surgery between 1995 and 2005.

RESULTS: Between 1995 and 2005, the annual number of knee arthroplasties in patients
with a primary diagnose of OA increased from 4,916 to 14,565, an increase of 196%.
The total number of hip arthroplasties increased from 13,785 to 20,715, an increase
of 50%. The demographical projection suggests that the number of total hip arthroplasties
will increase to 31,731 by 2030, an increase of 53%, and the number of knee arthroplasties
to 22,183. The trend projection suggests that the numbers may increase to 51,680
for the hip (+149%) and to 57,893 for the knee (+297%).

CONCLUSION: The increase in the number of knee and hip arthroplasties due to OA will
probably continue in the coming 20 years. The following developments will probably
contribute to this: demographical changes, the increase in overweight, improved long-term
outcomes of arthroplasty, more active lifestyle of the elderly and the increasing
number of orthopaedic surgeons.

2. Changes in surgical loads and economic burden of hip and knee replacements in
the US: 1997-2004.

Arthritis Rheum. 2008 Apr 15;59(4):481-8.

Kim S.

Robert Stempel School of Public Health, Florida International University, Miami,
FL 33199, USA.

Abstract: OBJECTIVE: A major component of the economic burden associated with the
treatment of arthritis relates to surgical joint replacements of the hips/knees.
The purpose of this study was to describe the recent trend of hip/knee replacements
and the associated economic burden.

METHODS: The Nationwide Inpatient Survey from 1997 to 2004 was analyzed. The International
Classification of Diseases, Ninth Revision, Clinical Modification procedure coding
was used to identify joint replacement cases.

RESULTS: During 2004, approximately 225,900 (95% confidence interval [95% CI] 201,782-250,018)
primary hip replacements and 431,485 (95% CI 397,454-465,516) primary knee replacements
were performed. This was a 37% increase in primary hip replacements and a 53% increase
in primary knee replacements compared with 2000. The number of primary replacement
procedures increased equally for males and females; however, the number of procedures
increased excessively among persons age 45-64 years. While Medicare remained the
major source of payment (55.4% for primary hip replacements, 59.3% for primary knee
replacements), private insurance payment experienced a steeper increase. In 2004,
the national bill of hospital charges for hip/knee replacements was $26.0 billion,
the hospital cost was $9.1 billion, and the amount of reimbursement was $7.2 billion
(28% of hospital charges or 79% of hospital cost). Nearly 600,000 hip replacements
and 1.4 million knee replacements will be performed in the year 2015.CONCLUSION:
The number of joint replacement procedures performed is growing faster than ever.
The health care community should consider and prepare for this upcoming demand of
surgical loads and its associated economical burden.

3. Prevalence of primary and revision total hip and knee arthroplasty in the United
States from 1990 through 2002.

Abstract: BACKGROUND: The purpose of this study was to quantify the procedural rate
and revision burden of total hip and knee arthroplasty in the United States and to
determine if the age or gender-based procedural rates and overall revision burden
are changing over time.

METHODS: The National Hospital Discharge Survey (NHDS) for 1990 through 2002 was
used in conjunction with United States Census data to quantify the rates of primary
and revision arthroplasty as a function of age and gender within the United States
with use of methodology published by the American Academy of Orthopaedic Surgeons.
Poisson regression analysis was used to evaluate the procedural rate and to determine
year-to-year trends in primary and revision arthroplasty rates as a function of both
age and gender.

RESULTS: Both the number and the rate of total hip and knee arthroplasties (particularly
knee arthroplasties) increased steadily between 1990 and 2002. Over the thirteen
years, the rate of primary total hip arthroplasties per 100,000 persons increased
by approximately 50%, whereas the corresponding rate of primary total knee arthroplasties
almost tripled. The rate of revision total hip arthroplasties increased by 3.7 procedures
per 100,000 persons per decade, and that of revision total knee arthroplasties, by
5.4 procedures per 100,000 persons per decade. However, the mean revision burden
of 17.5% for total hip arthroplasty was more than twice that for total knee arthroplasty
(8.2%), and this did not change substantially over time.

CONCLUSIONS: The number and prevalence of primary hip and knee replacements increased
substantially in the United States between 1990 and 2002, but the trend was considerably
more pronounced for primary total knee arthroplasty.

CLINICAL RELEVANCE: The reported prevalence trends have important ramifications with
regard to the number of joint replacements expected to be performed by orthopaedic
surgeons in the future. Because the revision burden has been relatively constant
over time, we can expect that a greater number of primary replacements will result
in a greater number of revisions unless some limiting mechanism can be successfully
implemented to reduce the future revision burden.

4. Total hip arthroplasty in Denmark: incidence of primary operations and revisions
during 1996-2002 and estimated future demands.

Abstract: BACKGROUND: The annual number of total hip arthroplasties (THA) has increased
in Denmark over the past 15 years. There is, however, limited detailed data available
on the incidence of THAs.

METHODS: We calculated the incidence rates (IR) of primary THA and revision in Denmark
between 1996 and 2002 and estimated the demands for primary THA in Denmark until
2020. We used data from the Danish Hip Arthroplasty Registry, a nationwide and population-based
clinical database, to identify patients who had undergone primary THA (n = 37,144)
or revision arthroplasties (n = 6446). Age and sex-specific data on the Danish population
were obtained from the StatBank Denmark. All IRs were standardized according to two
standards, i.e. the Danish population in 1996 and the European standard population
(18 age groups). The future demands for primary THA were estimated using the age
and sex-specific incidence of primary THA for 2002 as a reference, and taking into
account the expected changes in the age distribution of the population and the trend
in IRs seen in Denmark between 1996 and 2002.

RESULTS: The annual overall standardized IRs of primary THAs and revisions increased
from 101 (95% confidence interval (CI): 97.6-104) to 134 (CI: 131-138) and from 19.2
(CI: 17.9-20.5) to 21.1 (CI: 19.8-22.4) per 100,000 inhabitants from 1996 to 2002,
respectively (IRs adjusted to the Danish population in 1996). The IRs of primary
THAs and revisions increased by 30% and 10% during this period. The relative increase
in IRs of primary THAs was found to be similar in both women and men. The increase
was higher among patients aged 50-59 years, however. Furthermore, a decrease in IRs
was seen in patients who underwent primary THA due to rheumatoid arthritis. IRs of
primary THAs have been estimated to increase by 22% in 2020 compared with 2002, based
only on the expected changes in the age distribution of the population. However,
assuming that the annual age and sex-independent increase in the IRs seen in the
period 1996-2002 will continue, the IR of primary THA is estimated to increase by
as much as 210% in 2020.

INTERPRETATION: The overall annual standardized IRs of primary THAs and revisions
in Denmark increased during the period from 1996 to 2002. Moreover, the demands for
THA procedures in the coming decades may exceed the current capacity due to the ageing
population and a continued age and sex-independent increase in surgical activity.

This is a porous structure made of Tantalum and has better bone-ingrowth potential.
This is often useful in revision situations where there is poor bone stock and also
can used as wedges and augments to be used instead of structural bone grafts.